In my house a small server PC has been running for some years. It was my old desktop PC which I have equiped with a DVB-S-TV card, installed a Linux and used it as a video disk recorder and a file server. During the years more and more services have been added. Now, the computing power is no longer sufficient (mainly because, we now use video streaming) and the hard disk space is always too small and the system doesn’t support newer hard disks. The server must be renewed.
The new server should provide the following services:
- Fileserver, NAS for all PC of the family
- Video recorder, which is programmable via a web interface and can stream the current program as well as the recordings in the local network ( to one of my dbox2 clients or to a PC), later also in HD
- Database und host for my web based ham radio log program
- Linux-Server, which I can use from my Windows-PC with a X-Terminal
- Running long term computing applications like transcoding of videos or some upload or download tasks
For those who don’t know a dbox2: It’s an old settop box for pay-TV which was very widespread in Germany. Now the old boxes can be bought very cheap on ebay because in the meantime they are all replaced by HD-compatible boxes. For the dbox2 exists several Linux images which can be used as a nead alternative for the original firmware. The dbox-Linux has also a client for receive streams of my VDR software.
The different services and the different users make it difficult to power down the server i the meantime. I have a IP-switch solution on the stack but the useability will not be sufficient for the family. Perhaps later… Now i need a system suitable for continuous running with a potentially low power consumption.
Therefore, the question is: How do I get a powerfull enough system with a as low as possible power consumption. The new server should be much more powerfull as the old one but the power consumption – especially in idle mode – should be less.
Selection of the system
In the last time there was a significant movement in the chip technology regarding the power consumption. Intel as well as AMD introduces new desktop processor families which are optimized for power consumption and in the embedded computing edge exists countless solutions which are power efficient but slow. And Linux can also be installed on the very efficient ARM processor family. Because I need a PCI slot for my DVB-S card and significant computing power I can only use a common PC solution. The new processor families from Intel (Sandy-Bridge) and AMD are fast, yet efficient and have integrated graphic units. That’s what I’m looking for. Sandy-bridge is more powerfull but has less power consumption as the AMD alternatives, so the choice was not difficult.
The c’t magazine for computer technique has tested mainboards for the new Sandy-Bridge architecture and found the Intel DB65AL board outstanding power efficient for that class. This board has all what I need and is not expensive. That’s it. The choice of the processor is not so easy. At the low end of computing power, all processors of the Celeron, the old and the new Sandy-Bridge architecture have nearly the same idle power consumption. (following c’t). I voted for the more expensive but more powerfull new core i3-2100.
To allow the power down of the hard disk, if it is not used, I add a small and cheap SSD of 8GB for the operating system. This has the additional advantage that the data and the system disk can be changed independently which makes later service much more easy.
So, my new server consists of
- a Intel DB65AL Mainboard
- Core i3-2100 Processor with integrated graphic unit
- be-Quiet 80+ 350W-power supply
- 2 TB Samsung ecoGreen hard disk
Measurement of the power consumption
My old (now 13 years old ) system with an AMD K6-266, ASUS SP98 Mainboard, two IDA hard disks and the DVB-S-TV card (TechnoTrend Rev. 1.3) has the following power consumption:
|typical load||65 W|
The typical load is the streaming of a VDR recording which has partially a CPU load of 100 %.
For a better comparision here are the idle-power consumptions of some other PCs:
|core-i5-720, Intel DH55HC, NVidia GeForce 8400 DX graphic, 1HDD||51 W|
|IBM ThinkCentre with Pentium 4, 2.6 GHz, 1HDD||47 W|
|AMD Athlon64 1.8 GHz (cool’n quiet), MSI K8T Mainboard, on-board graphic, 1HDD||74 W|
|AMD Athlon64X2 2.31 GHz, Gigabyte MA78GM, on-board graphic, 1HDD||61 W|
|Notebook ThinkPad T400 with core2Duo-P8700 (screen as dark as possible)||15 W|
|typical NAS-System without hard disks (add typ. 5-10W for each hdd)||15-20 W|
My new server consumes the following power:
|Base system, idle||27 W|
|Base system, running hdd||32 W|
|Base system, idle, with DVB-S card||38 W|
|Base system with DVB-S card, load 1 Core 100%, running hdd||51 W|
The plain PC needs 27 W in idle mode what is IMHO frugal. By undervolting this can propably be lowered slightly. A pure power sink the DVB-S-TV card. It’s no surprise because of the card becomes warm and has to supply also the LNC at the dish.
Summarized I was able to reduce the power consumption by over 10W and have much much more computional power and disk space. But because of the DVB-S card the system at all is no power saving wonder.
Yet lower power consumption?
To further reduce the power consumption it is necessary to power down the server in unused periods. To to this without lost of comfort the system can be splitted to two servers: a video server wich provides also the high computational tasks and sleeps during unused periods and a small and very power efficient ARM-based system for the 24/7 running services (file server, FTP, data base etc.). But such a second small system would cost another 200-300 EUR.